The supply is controlled at the intake by a Consumer's Service Unit, which consists of a large main double pole switch combined with a single pole fuse or an earth leakage contact breaker for each of the lighting circuit, cooker circuit, water heater circuit and ring circuit.

In modern domestic installations the power circuits are tapped off a ring circuit. This is a cable which passes through the various rooms of the house and has both pairs of conductors connected to one fuse. There are therefore two paths to any particular circuit. Each appliance in the circuit is fitted with a fuse.

All fuses are placed in the live side of the supply ensuring that if a fuse blows the circuit is dead and it is not possible to receive an electric shock.